(1) Field of the Invention
The present invention relates to underwater detection of own platform or other than own platform acoustic signals and more particularly to a Tactical Expendable Device (TED) for use by submarines, surface ships and helicopters for short range target detection under ambient noise conditions, RF communications or monitoring of own platform noise.
(2) Description of the Prior Art
It is well known that the normal method of acoustic detection for submarines, surface ships or helicopters is a general purpose active or passive sonar system including hydrophone elements, cabinets of electronic circuitry and one or more displays manned by full-time sonar operators. These sonar systems, which include hull mounted, suspended and towed arrays, acquire detection at the greatest possible range consistent with ships self noise, e.g., flow noise, propeller noise, machinery noise, etc., environmental conditions and propagation paths existing at that time and place. Suspended and towed arrays however are not carried by all ASW platforms and even when carried, cannot always be conveniently deployed in every situation. In addition, all of these types of sonar systems have operational limitations.
Flow noise and own platform propulsion noise unavoidably increase with platform speed, thus degrading sonar performance. At the highest platform speeds, high noise levels eliminate much or all of the directivity gains achieved by using a multielement array over a single hydrophone in an ambient noise background. Also, improved performance of sonar systems tends to be directly correlated to increased physical size and consequently to increase weight. Thus, there are upper limits in performance and detection range which can be provided to an ASW platform by a general purpose system. In addition, an array necessarily has some acoustic distortion or blind spots because of array location, design or nature of the dome, presence of other structures around it, and the need to baffle it from propulsion machinery or noise sources aboard the platform. For example, hull mounted arrays are generally blind to stern arrivals while the performance of towed arrays is degraded by own platform noise. Furthermore, no existing arrays can monitor own platform noise or active sonar systems in the far field.
The TED not only supplements these systems by providing additional capability where these systems have limitations but also provides new capabilities.